1. Field of the Invention
The invention relates to a method for building a radial tire on a tire-building machine that has an expandable carcass drum with a cylindrical external circumference and two bellows supports with inflatable bellows. A tire inner liner and a carcass ply have projections and project beyond the edges of the carcass drum which are laid and spliced on the carcass drum. Subsequently bead cores with core profiles are positioned and the lateral projections of the carcass ply are turned up around the outsides of the bead cores and the core profiles by the inflation of the bellows.
The invention further relates to a device for building a radial tire that has an inner liner, a carcass ply, bead cores with core profiles and sections of the carcass ply turned up around the bead cores and forming turn-ups. The device has an expandable carcass drum having a cylindrical outer surface and two bellows supports with inflatable bellows.
2. Discussion of Background Information
It is customary to use single-step or two-step tire-building machines for building radial tires. Two-step tire-building machines are known which operate according to the finger ply down method or an expansion drum method. With a two-step method, on the first step of the tire-building machine, the inner liner and subsequently the carcass ply are laid and spliced on an expandable carcass drum having a cylindrical external circumference. The bead cores together with core profiles are placed with the drum being expanded. This is followed by turning up the projections of the carcass ply projecting beyond the carcass drum around the bead cores and the core profiles, which is carried out with the aid of inflatable bellows. After optional further tire components are placed and sidewall profiles are placed and rolled, the tire carcass is completed and is removed from the now retracted carcass drum. The tire carcass is transported to a second building drum via a transfer device. On a separate belt drum the belt plies are completed to form the belt assembly and subsequently the one-part or multiple-part tread rubber is applied. A transfer device transports the belt/tread rubber assembly to the tire carcass and positions it over the carcass. The tire carcass is joined to the belt/tread rubber assembly by shaping and connected by rolling. With a single-step method, the production of the carcass and the completion of the green tire are carried out by finishing with the belt/tread rubber assembly on a single drum.
The bellows supports arranged at the side of the carcass drum are usually embodied such that the outsides of the uninflated bellows resting thereon are located on a cylindrical surface, the diameter of which is smaller than that of the external surface of the carcass drum in order to be able to position the bead cores together with core profiles at defined positions. The smaller diameter on the sides of the load-bearing surface formed by the carcass drum and the bellows for the inner liner and the carcass ply in these areas permits only a localized support of those rollers that are customarily used during the placing and splicing of these plies. Attempts have therefore been made to provide a more advantageous load-bearing surface for the inner liner and the carcass ply by inflating the bellows. However, the load-bearing surface resulting thereby is very irregular and a large gap forms between the carcass drum and the bellows so that there is a great risk of air pockets forming between the inner layer and the carcass ply.